Mechaniczno Biologiczna Wastewater Treatment Plant, Trześń, Podkarpackie, Poland

Mechaniczno Biologiczna is a wastewater treatment plant located in Trześń, a village in the Podkarpackie Voivodeship of southeastern Poland. The plant serves a population of 1,626 and is part of the municipal infrastructure for the local community. It operates under Polish regulations which transpose the EU Urban Waste Water Treatment Directive. The plant provides secondary treatment, which is the standard biological treatment required for agglomerations of this size under EU Directive 91/271/EEC. The designed capacity is 6,400 m³/day, and the current discharge volume is 231.84 m³/day, indicating ample capacity for current loads. The plant's treatment process is mechanical-biological, as indicated by its name. Treated effluent is discharged into local waterways that drain into the Vistula River basin, ultimately reaching the Baltic Sea. The plant plays a key role in protecting the region's water quality, supporting aquatic life in the downstream rivers and contributing to the ecological health of the Baltic Sea catchment.

The plant discharges into local streams that are part of the Vistula River basin, Poland's largest river system. The Vistula flows northward into the Baltic Sea, a semi-enclosed sea sensitive to nutrient pollution. The plant's secondary treatment helps reduce organic load and nutrients, mitigating eutrophication risks in downstream waters and supporting biodiversity in the riverine ecosystem.